Transmission of multiplex protocol data units in physical layer packets

ABSTRACT

A transmitter generates MUX-PDUs for video, audio, data, and/or control streams based on a fixed PHY packet size such that all or a substantial percentage of the MUX-PDUs conform to the PHY packet size. The MUX-PDUs have variable sizes and are mapped to PHY packets such that (1) each MUX-PDU that is smaller than the PHY packet size is sent in one PHY packet and (2) each MUX-PDU that is larger than the PHY packet size is sent in a minimum number of PHY packets. Each MUX-PDU is padded with one or more null MUX-PDUs and/or one or more padding bytes, if needed, to obtain the PHY packet size. Each PHY packet is sent in one transmission time interval (TTI) to a receiver. The receiver performs the complementary processing on the received PHY packets to recover the MUX-PDUs. The receiver forwards each valid MUX-PDU and discards any padding.

BACKGROUND

I. Field

The present invention relates generally to communication, and morespecifically to techniques for transmitting and receiving multiplexprotocol data units (MUX-PDUs) in a wireless communication system.

II. Background

Wireless communication systems are widely deployed to provide variouscommunication services such as voice, video, packet data, and so on.These systems may be multiple-access systems capable of providingcommunication for multiple users by sharing the available systemresources (e.g., the system bandwidth and/or transmit power). Examplesof such multiple-access systems include a Code Division Multiple Access(CDMA) system, a Time Division Multiple Access (TDMA) system, aFrequency Division Multiple Access (FDMA) system, and an OrthogonalFrequency Division Multiple Access (OFDMA) system.

Videophone or video telephony is a rapidly growing application for manywireless communication systems. A videophone application transmits voiceand video simultaneously using, for example, ITU-T Recommendation H.223(or simply, “H.223”), entitled “Multiplexing Protocol for Low Bit RateMultimedia Communication.” H.223 is a protocol that receives video,audio, data, and control as separate media streams and generatesMUX-PDUs for all of these streams. The MUX-PDUs are then mapped to, orencapsulated within, PHY packets, which are packets at a physical layer(PHY). The PHY packets are further processed and transmitted via awireless channel to a receiver.

The receiver typically receives some percentage of PHY packets in errordue to noise and impairments in the wireless channel. The PHY packetsreceived in error are often called erased PHY packets. Typically, allMUX-PDUs carried in the erased PHY packets are also lost. Since erasedPHY packets are inevitable for a wireless system, there is a need in theart for techniques to reduce the number of lost MUX-PDUs due to theerased PHY packets.

SUMMARY

Techniques for efficiently sending MUX-PDUs in PHY packets in a wirelesscommunication system are described herein. The PHY packets may have afixed size that may be configured or selected during call setup. TheMUX-PDUs are generated based on the PHY packet size such that all or asubstantial percentage of the MUX-PDUs conform to the PHY packet size.For example, a video encoder may encode a video signal to generate codedvideo slices, and each video slice may be sent in one MUX-PDU. An audioencoder may encode an audio signal to generate coded audio packets, andone or more audio packets may be sent in one MUX-PDU. Each MUX-PDU thatconforms to the PHY packet size is sent in one PHY packet.

At a transmitter, MUX-PDUs are generated for multiple media streams(e.g., video, audio, data, and/or control streams) based on the PHYpacket size. The MUX-PDUs have variable sizes and are mapped to PHYpackets such that (1) each MUX-PDU that is smaller than the PHY packetsize is sent in one PHY packet and (2) each MUX-PDU that is larger thanthe PHY packet size is sent in a minimum number of PHY packets. EachMUX-PDU is padded with one or more null MUX-PDUs and/or one or morepadding bytes, if needed, to obtain the PHY packet size. The padding isselected such that it is not mistaken for a MUX-PDU header or validdata. Each PHY packet may be sent in one transmission time interval(TTI) to a receiver.

The receiver performs the complementary processing on the received PHYpackets to recover the MUX-PDUs. The receiver forwards each validMUX-PDU and discards any padding encountered. The receiver furtherdemultiplexes the video, audio, data, and control in the recoveredMUX-PDUs onto their respective media streams.

Various aspects and embodiments of the invention are described infurther detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and nature of the present invention will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings in which like reference charactersidentify correspondingly throughout.

FIG. 1 shows the processing and multiplexing at a transmitter for avideophone call.

FIG. 2 shows the structure of a MUX-PDU.

FIG. 3 shows the mapping of MUX-PDUs to PHY packets without alignment.

FIG. 4 shows the mapping of MUX-PDUs to PHY packets with alignment.

FIG. 5 shows a 5-byte padding pattern.

FIG. 6 shows a process to generate an aggregate MUX-PDU with one or moresmaller MUX-PDUs and padding.

FIG. 7 shows a PHY packet that contains one MUX-PDU, multiple nullMUX-PDUs, and multiple padding bytes.

FIG. 8 shows a block diagram of a transmitter and a receiver.

DETAILED DESCRIPTION

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any embodiment or design described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments or designs.

FIG. 1 shows a block diagram of the processing and multiplexing at atransmitter for a videophone call using ITU-T Recommendation H.324M (orsimply, “H.324M”). H.324M is a modified version of ITU-T RecommendationH.324, entitled “Terminal for Low Bit Rate Multimedia Communication.”H.324 is an international standard for multimedia communication on a lowbit rate circuit-switched system and utilizes H.223 as a datatransfer/multiplexing protocol.

At an application layer 110, the videophone call is processed asseparate video, audio, data, and control signals that are sent ondifferent logical channels. The data may be for text or some othercontent. Each logical channel is identified by a unique logical channelnumber (LCN). LCN 0 is used for the control channel. The number oflogical channels to use for the videophone call and the content to becarried by each logical channel are defined during call setup.

A video encoder 122 processes a video signal from video input/output(I/O) 112 and provides a coded video stream. An audio encoder 124processes an audio signal from audio I/O 114 and provides a coded audiostream. A data signal from an application 116 is processed by a dataprotocol (block 126) to generate a data stream. A control signal fromapplication 116 is processed in accordance with an ITU-T RecommendationH.245 (or simply, “H.245”), entitled “Control Protocol for MultimediaCommunication” (block 128), and further processed in accordance with aSimple Retransmission Protocol (SRP) (block 130) to generate a controlstream.

H.223 includes an adaptation layer 140 and a multiplex layer 150.Adaptation layer 140 receives and processes the video, audio, data, andcontrol streams separately. Adaptation layer 140 adds information toeach media stream, if applicable, for error detection and/or errorcorrection, sequence numbering, and retransmission. Adaptation layer 140generates adaptation layer service data units (AL-SDUs) for each mediastream. Each AL-SDU for the video stream may carry coded video for oneframe, one slice, or some other unit of video. A video slice correspondsto some number of rows and some number of columns of a video frame. EachAL-SDU for the audio stream typically carries up to three audio packetssince more bundled audio packets will increase delays.

Multiplex layer 150 receives the AL-SDUs for all media streams andgenerates MUX-PDUs having variable lengths. Each MUX-PDU may carry datafrom one or more AL-SDUs for one or more media streams. For example, asingle MUX-PDU may carry a combination of video, audio, and control.Multiplex layer 150 performs multiplexing in accordance with a multiplextable that contains up to 16 entries for up to 16 different MUX-PDUformats. Each MUx-PDU format indicates the number of bytes (if any) tobe carried for each media stream in one MUX-PDU. Each MUX-PDU is in oneof the formats indicated in the multiplex table. The multiplex table isdefined during call setup and may be updated during the call.

A physical layer 160 receives the MUX-PDUs and generates PHY packets (orsimply, “packets”). The processing by physical layer 160 is dependent onthe system design and typically includes encoding, interleaving, symbolmapping, and so on. The PHY packets are transmitted via a wirelesschannel to a receiver.

For H.223, the transmitter multiplexes video, audio, data, and H.245control into MUX-PDUs and sends these MUX-PDUs to the receiver. Thereceiver receives the MUX-PDUs and demultiplexes the video, audio, data,and control sent in these MUX-PDUs onto their separate media streams.The MUX-PDUs are the lowest level data units known to the videophoneapplication. The videophone application typically has no knowledge ofhow the MUX-PDUs are transmitted by the physical layer.

FIG. 2 shows the structure of a MUX-PDU in accordance with level 2protocol of H.223. The MUX-PDU is preceded by a 2-byte level 2 flag thatmay be set to one of two 2-byte values given by H.223. The level 2 flagdelimits or borders each MUX-PDU and is used by the receiver to detectfor a new MUX-PDU.

For level 2, the MUX-PDU includes a 3-byte header followed by avariable-size payload. The MUX-PDU header includes a 4-bit multiplexcode (MC) field, an 8-bit multiplex payload length (MPL) field, and a12-bit parity bits field. The MC field indicates the format of theMUX-PDU, which is one of the MUX-PDU formats defined in the multiplextable. The MPL field indicates the size of the MUX-PDU payload. Theparity bits field carries 12 parity bits generated for the MC field andthe MPL field. The MUX-PDU payload has a variable size that ranges from0 to 254 bytes and is indicated by the MPL field.

H.223 covers multiplexing of media streams for a circuit-switchedapplication. Such an application typically relies on the physical layerto provide a dedicated connection and a fixed data rate for a call. Themedia streams typically have data rates that may vary widely over time.The multiplexing techniques described herein efficiently multiplexMUX-PDUs onto PHY packets.

The multiplexing techniques described herein may be used for variouswireless communication systems that support circuit-switchedapplications. One such system is a Wideband-CDMA (W-CDMA) system that isdescribed in documents from a consortium named “3^(rd) GenerationPartnership Project” (3GPP). In W-CDMA, higher layer data may be sent inone or more transport channels such as, for example, a dedicated trafficchannel (DTCH) and a dedicated control channel (DCCH). Each transportchannel is associated with one or more transport formats, which may beselected during call setup. Each transport format specifies variousprocessing parameters such as (1) the transmission time interval (TTI)for the transport channel, (2) the size of each transport block of data,(3) the number of transport blocks to be sent in each TTI, (4) thelength of each code block, (5) the coding scheme to use for the TTI, andso on. Only one TTI is used for each transport channel, and the selectedTTI may span one, two, four, or eight frames. Each frame is a 10millisecond (ms) time interval that is identified by a system framenumber (SFN).

A transport format that is commonly used for a videophone call has thefollowing parameters: a data rate of 64 kilobits/second (kbps), a TTI ofeither 20 ms or 40 ms, and one transport block per TTI. The transportblock for each TTI may be considered as a PHY packet. Each PHY packetcarries 160 bytes for the 20 ms TTI and 320 bytes for the 40 ms TTI. Asingle transport format may be used for the videophone call, and the PHYpacket size is then fixed for the duration of the call.

FIG. 3 shows the mapping of MUX-PDUs to PHY packets without alignment.For this non-aligned mapping scheme, each MUX-PDU is sent in as many PHYpackets as needed and starting at the first available byte in the nextPHY packet to be sent. If the MUX-PDU size ranges from 0 through 254bytes and if the PHY packet size is fixed at 160 bytes, then eachMUX-PDU may be sent in one or two PHY packets. Furthermore, a given PHYpacket may carry multiple MUX-PDUs. For example, PHY packet 4 carriesthe tail portion of MUX-PDU 2 and the beginning portion of MUX-PDU 3.

The receiver receives the PHY packets and decodes each received PHYpacket separately. Each PHY packet that is decoded correctly is passedup to the multiplex layer for processing and reassembly. Each PHY packetthat is decoded in error (or erased) is discarded. Due to noise andimpairments in the wireless channel, the error rate or the percentage oferased PHY packets may be relatively high. For each erased PHY packet,all of the MUX-PDUs carried by that erased PHY packet may be discarded.For example, if PHY packet 4 is decoded in error, then the entireMUX-PDU 3 is discarded since its header is lost in PHY packet 4, and theentire MUX-PDU 2 may also be discarded since its tail portion ismissing. The amount of data that is lost at the multiplex layer is morethan the amount of data that is lost by the physical layer because ofnon-alignment of the MUX-PDUs and the PHY packets for the two layers.

FIG. 4 shows the mapping of MUX-PDUs to PHY packets with alignment. Forthis aligned mapping scheme, the MUX-PDUs are generated and mapped suchthat, all or most of the time, each MUX-PDU is sent in one PHY packet.This mapping scheme allows each PHY packet that is decoded correctly tobe fully used by the multiplex layer at the receiver. This scheme alsominimizes the occurrence of the situation whereby more than one PHYpacket worth of data is lost in the multiplex layer when only one PHYpacket is decoded in error. Each MUX-PDU may be sent starting with thefirst byte in a PHY packet, and the PHY packet boundary is then alignedwith the MUX-PDU boundary. In certain instances, it may not be possibleto fit a large MUX-PDU into one PHY packet. In such instances, the largeMUx-PDU may be sent in a minimum number of PHY packets.

The MUX-PDU formats and sizes are selected based on the PHY packet size.The video encoder may be designed based on the selected MUX-PDU size.For example, the video encoder may be capable of encoding a frame ofvideo or a slice of video. Since a video decoder is able toindependently decode each video slice, each MUX-PDU may carry one ormore complete video slices. This may be achieved by (1) designing thevideo encoder to send one video slice at a time to the adaptation layerand (2) designing the adaptation and multiplex layers to attempt to fitone or more complete video slices into each MUX-PDU. The audio encodermay also be designed based on the selected MUX-PDU size to generatecoded audio packets that can be sent in one PHY packet. The multiplexlayer may thus be designed or customized based on the PHY packet size.

In most cases, the MUX-PDUs will be smaller than the PHY packet size. Inthese cases, a PHY packet may carry a single MUX-PDU, multiple MUX-PDUs,a single MUX-PDU with padding or stuffing, or multiple MUX-PDUs withpadding. The multiplex layer may be designed to generate “aggregate”MUX-PDUs. Each aggregate MUX-PDU has the same size as the PHY packetsize, carries one or more MUX-PDUs and padding (if needed), and is sentin one PHY packet.

FIG. 5 shows a 5-byte padding pattern 500 that may be used for padding aMUx-PDU that is smaller than the PHY packet size. Padding pattern 500includes five bytes. The first two bytes of padding pattern 500 are forthe level 2 flag. The last three bytes of padding pattern 500 are for aMUX-PDU header that indicates a MUX-PDU payload size of zero (e.g., aMUx-PDU header of 0x00, 0x00, and 0x00, where ‘0x’ denotes hexadecimalvalues to follow). Padding pattern 500 represents a “null” MUX-PDUhaving only a header and no payload (or a payload length of zero).Padding pattern 500 may be repeated as many times as needed until thePHY packet is completely or mostly filled. Other 5-byte padding patternsmay also be used for padding (e.g., padding patterns formed with otherpossible 2-byte values for the level 2 flag).

Padding pattern 500 has a fixed length of five bytes. If the size of thearea to be padded is not a multiple of five bytes, then padding pattern500 will either overfill (overshoot) or underfill (undershoot) the area.To avoid overfilling/underfilling the area with padding pattern 500, aone-byte padding pattern may be used to pad a space that is smaller thanfive bytes. This one-byte padding pattern (which is also called apadding byte) may be 0xFF or some other byte value. In general, thepadding may be achieved using the 5-byte padding pattern, the one-bytepadding pattern, some other padding pattern, or any combination thereof.In general, any padding pattern may be used for padding as long as thereceiver will not interpret the padding pattern as a valid MUX-PDUheader or real data.

FIG. 6 shows a flow diagram of a process 600 to generate an aggregateMUX-PDU with one or more MUX-PDUs that are smaller than the PHY packetsize. Process 600 may be performed by the multiplex layer at thetransmitter. The aggregate MUX-PDU is sent in one PHY packet.

Initially, the aggregate MUX-PDU (or equivalently, the PHY packet) isfilled with a MUX-PDU (block 610). A determination is then made whetheranother MUX-PDU (e.g., the next MUX-PDU) can be sent in the PHY packet(block 612). If the answer is ‘Yes’, then the PHY packet is filled withthis MUX-PDU (block 614), and the process returns to block 612. Blocks612 and 614 fit as many MUX-PDUs as possible in the PHY packet.

If the answer is ‘No’ for block 612, then a determination is madewhether a null MUX-PDU (e.g., padding byte pattern 500) can sent in theremaining space in the MUX-PDU (block 616). If the answer is ‘Yes’ forblock 616, then a null MUX-PDU is appended in the PHY packet (block618), and the process returns to block 616. Blocks 616 and 618 pad theremaining space in the PHY packet with as many null MUX-PDUs aspossible.

If the answer is ‘No’ for block 616, then a determination is madewhether there is any space left in the PHY packet (block 620). If theanswer is ‘Yes’ for block 620, then the PHY packet is padded with theone-byte fill pattern (block 622), and the process returns to block 620.Otherwise, if the answer is ‘No’ for block 620, then the processterminates. Blocks 620 and 622 pad the remaining space in the PHY packetwith as many padding bytes as needed.

FIG. 7 shows an example aggregate MUX-PDU 700 that contains one validMUX-PDU, multiple null MUX-PDUs, and multiple padding bytes. Themultiplex layer at the receiver (or simply, the receiver multiplexlayer) receives the aggregate MUX-PDU from the physical layer, extractsthe header of the first MUX-PDU, ascertains the size of this MUX-PDUbased on its header, recovers the MUX-PDU, and sends the MUX-PDU up tothe adaptation layer. The receiver multiplex layer then extracts theheader for each null MUX-PDU sent in the aggregate MUX-PDU, recognizeseach null MUX-PDU based on its header, and discards each null MUX-PDU.The receiver multiplex layer then encounters the first padding byte,detects that this byte is not for a valid MUX-PDU, regards this byte asan error, and discards the byte. For each subsequent byte, the receivermultiplex layer continues to search for a valid MUX-PDU header anddiscards all padding bytes that it encounters. The use of the paddingbytes does not affect operation at the receiver multiplex layer.

FIGS. 6 and 7 show the case in which the first MUX-PDU is smaller thanthe PHY packet size. If the MUX-PDU is larger than the PHY packet size,then the MUX-PDU is sent in a minimum number (n) of PHY packets and then-th PHY packet is padded as described above in FIG. 6.

FIG. 8 shows a block diagram of an embodiment of a transmitter 810 and areceiver 850 capable of implementing the multiplexing techniquesdescribed herein. Transmitter 810 and receiver 850 may each be part of acellular phone, a handset, a subscriber unit, a mobile station, a userterminal, a wireless device, a modem, or some other apparatus.

At transmitter 810, a video encoder 822 receives and encodes a videosignal and provides a coded video stream to a transmit (TX) dataprocessor 826. An audio encoder 824 receives and encodes an audio signaland provides a coded audio stream to TX data processor 826. Encoders 822and 824 may perform encoding in accordance with H.324M or some otherstandard or design. TX data processor 826 receives the coded video andaudio streams from encoders 822 and 824, respectively, and data andcontrol streams from a controller 840. TX data processor 826 implementsthe adaptation and multiplex layers for H.223, processes the receivedmedia streams, and generates MUX-PDUs based on the PHY packet size. A TXPHY processor 828 performs processing for the physical layer, processes(e.g., encodes, interleaves, and modulates) the MUX-PDUs as specified bythe system, and generates PHY packets. A transmitter unit (TMTR) 830conditions (e.g., converts to analog, filters, amplifies, and frequencyupconverts) the PHY packets and generates a modulated signal, which istransmitted via an antenna 832.

At receiver 850, an antenna 852 receives the modulated signaltransmitted by transmitter 810 and provides a received signal to areceiver unit (RCVR) 854. Receiver unit 854 conditions (e.g., filters,amplifies, and frequency downconverts) the received signal, digitizesthe conditioned signal, and provides data samples. A receive (RX) PHYprocessor 856 processes (e.g., demodulates, deinterleaves, and decodes)the data samples and provides decoded PHY packets to an RX dataprocessor 858. RX PHY processor 856 also provides an indication of eachPHY packet that is decoded in error. RX data processor 858 implementsthe adaptation and multiplex layers for H.223 at the receiver andprocesses the decoded PHY packets. RX data processor 858 extracts validMUX-PDUs in each decoded PHY packet, performs error detection and/orcorrection (if applicable), discards null MUX-PDUs and padding bytes,and demultiplexes the video, audio, data, and control onto separatemedia streams. RX data processor 858 provides the recovered video streamto a video decoder 860, the recovered audio stream to an audio decoder862, and recovered data and control streams to a controller 870.

Video decoder 860 processes the recovered video stream and provides adecoded video signal. Audio decoder 862 processes the recovered audiostream and provides a decoded audio signal. Controller 870 processes therecovered data and control streams, provides decoded data, and generatescontrols to properly present the decoded video, audio, and data. Ingeneral, the processing by RX PHY processor 856, RX data processor 858,video decoder 860, audio decoder 862, and controller 870 iscomplementary to the processing performed by TX PHY processor 828, TXdata processor 826, video encoder 822, audio encoder 824, and controller840, respectively, at transmitter 810.

Controllers 840 and 870 also control the operation of various processingunits at transmitter 810 and receiver 850, respectively. Memory units842 and 872 store data and program codes used by controllers 840 and870, respectively.

The multiplexing techniques described herein may be implemented byvarious means. For example, these techniques may be implemented inhardware, software, or a combination thereof. For a hardwareimplementation, the processing units used to perform multiplexing at atransmitter may be implemented within one or more application specificintegrated circuits (ASICs), digital signal processors (DSPs), digitalsignal processing devices (DSPDs), programmable logic devices (PLDs),field programmable gate arrays (FPGAs), processors, controllers,micro-controllers, microprocessors, other electronic units designed toperform the functions described herein, or a combination thereof. Theprocessing units used to perform the complementary demultiplexing at areceiver may also be implemented within one or more ASICs, DSPs,controllers, and so on.

For a software implementation, the multiplexing techniques may beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. The software codes may be storedin a memory unit (e.g., memory unit 842 or 872 in FIG. 8) and executedby a processor (e.g., controller 840 or 870). The memory unit may beimplemented within the processor or external to the processor.

The previous description of the disclosed embodiments is provided toenable any person skilled in the art to make or use the presentinvention. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein but is to beaccorded the widest scope consistent with the principles and novelfeatures disclosed herein.

1. An apparatus in a wireless communication system, comprising: a firstprocessor operative to generate a plurality of multiplex protocol dataunits (MUx-PDUs) for a plurality of media streams, the MUX-PDUs havingvariable sizes selected based on a predetermined physical layer (PHY)packet size; and a second processor operative to map the plurality ofMUX-PDUs to a plurality of PHY packets such that each MUX-PDU that issmaller than the PHY packet size is sent in one PHY packet.
 2. Theapparatus of claim 1, wherein the first processor is operative toprocess each of the plurality of media streams such that all or asubstantial percentage of the plurality of MUX-PDUs conform to the PHYpacket size.
 3. The apparatus of claim 1, wherein the second processoris operative to map the plurality of MUX-PDUs to the plurality of PHYpackets such that each MUX-PDU that is larger than the PHY packet sizeis sent in a minimum number of PHY packets.
 4. The apparatus of claim 1,wherein the first processor is operative to pad each MUX-PDU with one ormore null MUX-PDUs, if needed, to obtain the PHY packet size.
 5. Theapparatus of claim 1, wherein the first processor is operative to padeach MUX-PDU with one or more padding bytes, if needed, to obtain thePHY packet size.
 6. The apparatus of claim 5, wherein the one or morepadding bytes are selected so that the padding bytes cannot beunmistaken for a MUX-PDU header or valid data.
 7. The apparatus of claim1, wherein the first processor is operative to encode a video signal togenerate coded video slices and to multiplex each coded video slice ontoone MUX-PDU.
 8. The apparatus of claim 1, wherein the first processor isoperative to encode an audio signal to generate coded audio packets andto multiplex each audio packet onto one MUX-PDU.
 9. The apparatus ofclaim 1, wherein the plurality of media streams are for a videotelephony call.
 10. The apparatus of claim 1, wherein the firstprocessor is operative to generate the plurality of MUX-PDUs inaccordance with ITU-T Recommendation H.223.
 11. The apparatus of claim1, wherein the wireless communication system is a Wideband-CDMA (W-CDMA)communication system.
 12. The apparatus of claim 1, further comprising:a transmitter unit operative to transmit each of the plurality of PHYpackets in one transmission time interval (TTI).
 13. A method of sendinga plurality of media streams in a wireless communication system,comprising: generating a plurality of multiplex protocol data units(MUX-PDUs) for the plurality of media streams, the MUX-PDUs havingvariable sizes selected based on a predetermined physical layer (PHY)packet size; and mapping the plurality of MUX-PDUs to a plurality of PHYpackets such that each MUX-PDU that is smaller than the PHY packet sizeis sent in one PHY packet.
 14. The method of claim 13, wherein thegenerating the plurality of MUX-PDUs comprises processing each of theplurality of media streams such that all or a substantial percentage ofthe plurality of MUX-PDUs conform to the PHY packet size.
 15. The methodof claim 13, wherein the mapping the plurality of MUX-PDUs to theplurality of PHY packets is further such that each MUX-PDU that islarger than the PHY packet size is sent in a minimum number of PHYpackets.
 16. The method of claim 13, wherein the generating theplurality of MUX-PDUs comprises padding each MUX-PDU with one or morenull MUX-PDUs, if needed, to obtain the PHY packet size.
 17. The methodof claim 13, wherein the generating the plurality of MUX-PDUs comprisespadding each MUX-PDU with one or more padding bytes, if needed, toobtain the PHY packet size.
 18. An apparatus in a wireless communicationsystem, comprising: means for generating a plurality of multiplexprotocol data units (MUX-PDUs) for a plurality of media streams, theMUX-PDUs having variable sizes selected based on a predeterminedphysical layer (PHY) packet size; and means for mapping the plurality ofMUX-PDUs to a plurality of PHY packets such that each MUX-PDU that issmaller than the PHY packet size is sent in one PHY packet.
 19. Theapparatus of claim 18, wherein the means for generating the plurality ofMUX-PDUs comprises means for processing each of the plurality of mediastreams such that all or a substantial percentage of the plurality ofMUX-PDUs conform to the PHY packet size.
 20. The apparatus of claim 18,wherein the means for mapping the plurality of MUX-PDUs to the pluralityof PHY packets is further such that each MUX-PDU that is larger than thePHY packet size is sent in a minimum number of PHY packets.
 21. Theapparatus of claim 18, wherein the means for generating the plurality ofMUX-PDUs comprises means for padding each MUX-PDU with one or more nullMUX-PDUs, if needed, to obtain the PHY packet size, and means forpadding each MUX-PDU with one or more padding bytes, if needed, toobtain the PHY packet size.
 22. A processor readable media for storinginstructions operable in a wireless device to: generate a plurality ofmultiplex protocol data units (MUx-PDUs) for a plurality of mediastreams, the MUX-PDUs having variable sizes selected based on apredetermined physical layer (PHY) packet size; and form a plurality ofaggregate MUX-PDUs with the plurality of MUX-PDUs such that each MUX-PDUthat is smaller than the PHY packet size is sent in one aggregateMUX-PDU, each aggregate MUX-PDU having the PHY packet size and beingsent in one PHY packet.
 23. A method of receiving a plurality of mediastreams in a wireless communication system, comprising: receiving aplurality of physical layer (PHY) packets of a predetermined size andcarrying a plurality of multiplex protocol data units (MUX-PDUs), eachPHY packet carrying one or more MUX-PDUs, and each MUX-PDU that issmaller than the predetermined size being sent in one PHY packet;processing each PHY packet to recover the one or more MUX-PDUs sent inthe PHY packet; and demultiplexing the plurality of MUX-PDUs obtainedfrom the plurality of PHY packets into the plurality of media streams.24. The method of claim 23, wherein the processing each PHY packetcomprises examining each header encountered in the PHY packet todetermine whether a valid MUX-PDU is being sent in the PHY packet, andforwarding each valid MUX-PDU found in the PHY packet.
 25. The method ofclaim 24, wherein the processing each PHY packet further comprises foreach header that is not for a valid MUX-PDU, determining whether theheader is for a null MUX-PDU, and discarding any null MUX-PDU.
 26. Themethod of claim 24, wherein the processing each PHY packet furthercomprises discarding any padding byte encountered in the PHY packet. 27.An apparatus in a wireless communication system, comprising: a firstprocessor operative to process data samples and provide a plurality ofphysical layer (PHY) packets of a predetermined size and carrying aplurality of multiplex protocol data units (MUX-PDUs), each PHY packetcarrying one or more MUX-PDUs, and each MUX-PDU that is smaller than thepredetermined size being sent in one PHY packet; and a second processoroperative to process each PHY packet to recover the one or more MUX-PDUssent in the PHY packet and to demultiplex the plurality of MUX-PDUsobtained from the plurality of PHY packets into a plurality of mediastreams.
 28. The apparatus of claim 27, wherein the second processor isoperative to examine each header encountered in each PHY packet todetermine whether a valid MUX-PDU is being sent in the PHY packet and toforward each valid MUX-PDU found in the PHY packet.
 29. The apparatus ofclaim 27, wherein the second processor is operative to discard anyheader for a non-valid MUX-PDU and each padding byte encountered in thePHY packet.
 30. An apparatus in a wireless communication system,comprising: means for receiving a plurality of physical layer (PHY)packets of a predetermined size and carrying a plurality of multiplexprotocol data units (MUX-PDUs), each PHY packet carrying one or moreMUX-PDUs, and each MUX-PDU that is smaller than the predetermined sizebeing sent in one PHY packet; means for processing each PHY packet torecover the one or more MUX-PDUs sent in the PHY packet; and means fordemultiplexing the plurality of MUX-PDUs obtained from the plurality ofPHY packets into a plurality of media streams.
 31. The method of claim23, wherein the means for processing each PHY packet comprises means forexamining each header encountered in the PHY packet to determine whethera valid MUX-PDU is being sent in the PHY packet, means for forwardingeach valid MUX-PDU found in the PHY packet, and means for discarding anynon-valid MUX-PDU and each padding byte encountered in the PHY packet.